The lines of communication in the nervous system consist of axonal and dendritic processes of nerve cells. The processes of one cell may communicate with those of another across synaptic clefts via chemical messengers that affect ionic currents in the cell membrane. If injury or disease causes the processes of the mammalian central nervous system to die, they normally do not regenerate, and communication is lost. The study of process communication and regeneration of mammalian central neurons would be aided by examining the detailed membrane properties of an identified cell in a controlled in vitro environment. This approach requires that the cells be isolated, unequivocally identified, and cultured. Cultures of solitary rat retinal ganglion cells, identified with specific fluorescent probes, are being developed in this laboratory. Preliminary studies have shown that process regeneration is enhanced by plating these cells on s specific monoclonal antibody against Thy-1 antigen, which is located on retinal ganglion cells. The specific aims of this proposal are-- (i) The study of intercellular communication by (a) characterizing the various ionic currents of the cell membrane using the patch-clamp technique; (b) testing the effects on these currents of neuroactive substances that may modulate intercellular communication and that are putatively found in amacrine cells that synapse on ganglion cells. These compounds include acetylcholine, GABA, glycine, dopamine, and many peptides such as substance P, somatostatin, TRH, and enkephalin. (ii) The study of process regeneration by (a) attempting to localize the binding of anti-Thy-1, which promotes process regeneration, at an ultrastructural level in the retina; (b) using an existing anti-idiotype against the Thy-1 antibody that will act as an analogue of Thy-1 in an attempt to identify a "naturally" occurring ligand that might recognize the Thy-1 determinant and influence process regeneration in the central nervous system; (c) using the knowledge gained of the specific ionic currents to pharmacologically block or enhance each current in order to affect process regeneration; (d) presenting normal target tissue (tectum and lateral geniculate nucleus) or extracts of these tissues to influence process regeneration; (e) attempting to increase the regeneration of optic nerve in vivo in adult rats by using the factors learned in culture in conjunction with medical nerve guides.